Thermoelectric elements that use thermoelectric semiconductor elements made of compounds such as bismuth/tellurium compounds, iron/silicon compounds, or cobalt/antimony compounds are used in applications such as cooling or heating devices and thermal power devices. Such a thermoelectric element is convenient as a cooling or heating source that does not use liquids or gases, takes up little space and is not subject to rotational friction, and does not require maintenance.
This thermoelectric element generally comprises two types of thermoelectric semiconductor element, p-type and n-type, arranged alternately in an array, with the thermoelectric semiconductor elements being connected to electrodes by soldering to form a ".pi."-shaped series circuit; the thermoelectric semiconductor elements and metal electrodes are sandwiched between ceramic substrates having metal films, and this assembly is widely used as a thermoelectric module.
A thermoelectric module that is known in the prior art is shown in FIG. 22. As shown in this figure, n-type thermoelectric semiconductor elements and p-type thermoelectric semiconductor elements 42 are arrayed alternately in a thermoelectric module 41 (in FIG. 22, only the thermoelectric semiconductor element at the right-hand end is given a reference number, as representative of a plurality of elements), and the n-type thermoelectric semiconductor elements and p-type thermoelectric semiconductor elements 42 are connected to electrodes 43. Upper and lower surfaces of the thermoelectric semiconductor elements 42 are connected alternately to the electrodes 43, so that all of the elements are eventually connected in series. The connections between the electrodes 43 and the thermoelectric semiconductor elements 42 are performed by soldering. The electrodes 43 on each of the upper and lower surfaces are connected to ceramic substrates 44 that are metallized with a metal such as copper or nickel, to fix the entire assembly together. The thus constructed thermoelectric element is usually called a thermoelectric module.
A power source is connected to electrodes of this thermoelectric module 41, and, when a current flows in the direction from each n-type element to a p-type element, the Peltier effect ensures that heat is absorbed by the upper portion of the ".pi." shape and heat is generated by the lower side thereof. Reversing the connection direction of the electrodes changes the directions in which heat is absorbed and generated. This phenomenon is utilized so that the thermoelectric element can be used in a cooling or heating device. Such a thermoelectric module is useful in a wide range of applications, from the cooling of devices such as computer CPUs and semiconductor lasers to use in insulated refrigerators.
Thermoelectric semiconductor elements of bismuth/tellurium compounds, which are representative of use in such thermoelectric modules, have a problem in that the crystals thereof tend to split at cleavage surfaces. Thus, in the prior art, grown monocrystals are first sliced and the sliced crystals are diced to form rectangular shapes of dimensions on the order of 1.5 mm.times.1.5 mm.times.2 mm, which are used in thermoelectric modules. Since the crystals split easily at the cleavage surfaces, the rectangular thermoelectric semiconductor elements are usually arrayed by hand, using tweezers, on a ceramic substrate that has been processed with a thin metal film, then, after being arrayed, the elements are soldered to metal electrodes. This means that the resultant thermoelectric module is extremely firm and lacks flexibility. The soldering itself also reduces flexibility, so the thermoelectric module is rigid. On top of that, the use of a ceramic substrate means that the thermoelectric module has no bendability or flexibility, and is stiff.
The dimensions of each thermoelectric semiconductor element are small at 1.5 mm.times.1.5 mm.times.2 mm, so that the dimensions of the thermoelectric element itself when it is put on the market as a commercial product are also extremely small at most approximately 40.times.40 mm or 60.times.60 mm.
Furthermore, since the thermoelectric semiconductor elements can break easily, a thermoelectric module is configured to have a high installation density of thermoelectric semiconductor elements on a ceramic substrate. The resultant surface area of the array of thermoelectric semiconductor elements (in other words, the cooling or heating surface area thereof) is small so that the efficiency thereof in cooling or heating a large surface area is extremely poor. In addition, the provision of supplementary equipment such as a heat sink or fan to radiate excess heat makes this module too large.
The prior-art thermoelectric module 41 is held together by a sandwich structure of the upper and lower substrates 44 made of ceramic, and thus the upper and lower substrates 44 are a vital part of the structure of the module. This means that the entire thermoelectric element is thick, and thus the thermal conductivity efficiency thereof is poor.
To improve the thermal conductivity in this case, experiments have been performed into using insulating films or flexible resin sheets as substrates, instead of ceramics. This use of a film or resin sheet as a substrate makes it possible to reduce the thickness of the substrates on which the thermoelectric semiconductor elements are installed, and, as a result, improve the thermal conductivity characteristics.
For example, a technique disclosed in Japanese Patent Application Laid-Open No. 3-137462 relates to the disposition of thermoelectric semiconductor elements on an insulating film substrate. With this technique, the density of thermoelectric semiconductor elements is fairly high. In addition, a pressure vessel is provided on a heat-absorbing side thereof, so the cooling or heating device is rigid.
Japanese Patent Application Laid-Open No. 7-202275 discloses a technique of using a copper plate attached to a resin sheet having flexibility and thermal resistance, as an electrode, and installing thermoelectric semiconductor elements on such an electrode. With this technique, the completed thermoelectric module is soldered fixedly to a copper plate over resin, so that the complete module is rigid and lacks flexibility.
In both cases, the objective is to reduce the total thickness of the thermoelectric element and increase the heat-transfer efficiency thereof. However, each of these techniques involves a high arrangement density of thermoelectric semiconductor elements, so that the entire thermoelectric element lacks flexibility. In other words, both applications give useful examples for improving the heat-transfer efficiency, but they do not disclose any techniques relating to flexible cooling or heating elements.
The present invention therefore provides a thermoelectric semiconductor chip unit, thermoelectric unit, and thermoelectric module wherein thermoelectric semiconductor crystals are not likely to split along cleavage surfaces.
This invention also provides a thermoelectric chip unit, thermoelectric unit, thermoelectric module, and thermoelectric sheet which has properties such as flexibility.
Furthermore, this invention provides a cooling or heatingdevice which has characteristics such that it can cover a large cooling or heating surface area, requires only compact supplementary equipment for radiating heat, and can be applied even to an objects having a complicated shape.